Display device

ABSTRACT

A display device includes an electronic paper display and a ground electrode. The electronic paper display is imageable by receiving charges on a charge receiving layer of the electronic paper display. The ground electrode is opposite to the charge receiving layer of the electronic paper display and exposed at an edge of the display device.

CROSS REFERENCE TO RELATED APPLICATIONS

This Application is a Continuation of U.S. patent application Ser. No.15/114,401, filed Jul. 27, 2016, entitled “DISPLAY DEVICE”, which is a371 U.S. National Stage Application of International Application No.PCT/US2014/014307, filed Jan. 31, 2014, entitled “DISPLAY DEVICE”, bothof which are incorporated herein by reference.

BACKGROUND

Electronic paper (“e-paper”) is a display technology designed torecreate the appearance of ink on ordinary paper. Some examples ofe-paper reflect light like ordinary paper and may be capable ofdisplaying text and images. Some e-paper is implemented as a flexible,thin sheet, like paper. One familiar e-paper implementation includese-readers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-sectional view of one example of a displaydevice.

FIG. 1B illustrates a top view of one example of the display deviceillustrated in FIG. 1A.

FIG. 2A illustrates a cross-sectional view of one example of a displaydevice.

FIG. 2B illustrates a top view of one example of the display deviceillustrated in FIG. 2A.

FIG. 3 illustrates a cross-sectional view of one example of anelectronic paper (“e-paper”) display.

FIG. 4 illustrates one example of a writing module.

FIGS. 5A-5C illustrate one example of a system including a writingmodule and a display device.

FIGS. 6A-6C illustrate one example of a system including a writingmodule and a display device.

FIGS. 7A-7C illustrate one example of a system including a writingmodule and a display device.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings which form a part hereof, and in which is shown byway of illustration specific examples in which the disclosure may bepracticed. It is to be understood that other examples may be utilizedand structural or logical changes may be made without departing from thescope of the present disclosure. The following detailed description,therefore, is not to be taken in a limiting sense, and the scope of thepresent disclosure is defined by the appended claims. It is to beunderstood that features of the various examples described herein may becombined, in part or whole, with each other, unless specifically notedotherwise.

Electronic paper (“e-paper”) is used in a variety of displayapplications such as signage, e-books, tablets, cards, posters, andpricing labels. E-paper has several paper-like features. For example,e-paper is a reflective display that uses ambient light as anillumination source. The ambient light strikes the surface and isreflected to the viewer. The usage of pigments similar to those that areused in printing allows the e-paper to be read at a wide range of anglesand lighting conditions, including full sunlight. The use of ambientlight also eliminates the need for illumination produced by the device,such as a backlight. This minimizes the power used by the e-paper. Inaddition, the e-paper does not use power to maintain the image. Once theimage is written, the image remains on the e-paper for an extendedperiod of time or until the e-paper is rewritten. Thus, a typicale-paper primarily uses power for changing the optical state of thee-paper.

E-paper is typically written by generating a charge on a surface inproximately to a layer of microcapsules that contain charged pigmentparticles. The charge on the surface attracts or repels the chargedpigment particles in the microcapsules to create the desired image. Towrite to e-paper, however, a writing module used to write to the e-paperhas to maintain a connection to a ground return path for the e-paper.

The following disclosure describes several examples of e-paper displaydevices that enable a secure electrical connection between a writingmodule and a ground return path of an e-paper display device. Theexample display devices also provide for controlled motion through awriting module, provide for proper spacing between the display devicesand a writing module, and provide mechanical robustness beyond thatprovided by the e-paper alone.

Accordingly, a display device, such as a gift card, prepaid card, creditcard, shelf tag, boarding pass, shipping label, etc., includes a passiveelectronic paper display. The electronic paper display is imageable byreceiving charges on an imaging surface of the electronic paper displayfrom a writing module. The display device includes a ground electrodeopposite to the imaging surface of the electronic paper display. Thedisplay device includes a ground access stripe on a surface of thedisplay device. The ground access stripe is electrically coupled to theground electrode. During writing of the electronic paper display, aconductive roller or brush of the writing module makes contact with theground access stripe to provide a ground return path that allows chargesreceived on the imaging surface to flow to the ground electrode as thewriting module and the display device are moved relative to each other.

FIG. 1A illustrates a cross-sectional view and FIG. 1B illustrates a topview of one example of a display device 100. Display device 100 includesa support structure 102, a ground electrode 104, an electronic paper(“e-paper”) display 106, and a ground access stripe 108. Ground accessstripe 108 is electrically coupled to ground electrode 104 through aconductor 110 within support structure 102. In this example, the viewingside of display device 100 is indicated by a viewer 122.

E-paper display 106 includes an imaging surface 114 and a surface 112opposite imaging surface 114. Surface 112 contacts ground electrode 104.Ground electrode 104 and e-paper display 106 are mounted on supportstructure 102 such that imaging surface 114 of e-paper display 106 isexposed. E-paper display 106 includes an active layer that switchescolor when a magnetic field or electrical charges are applied to imagingsurface 114. In one example, the active layer contains a switchablepigment or die combination. A resin or polymer may be used toencapsulate the active layer. In addition, e-paper 106 may include afunctional coating on the imaging surface 114. In one example, e-paperdisplay 106 has a thickness between 70 μm and 300 μm. One example ofe-paper 106 is further described below with reference to FIG. 3 .

Ground electrode 104 provides a counter-electrode for the imaging ofe-paper display 106 by a writing module. Ground electrode 104 allowscounter charges to flow to ground electrode 104 from a writing module.Thus, display device 100 remains basically charge neutral despitecharges being ejected onto imaging surface 114. Without a connectionbetween ground electrode 104 and the writing module, no appreciableamount of charges can be ejected onto imaging surface 114 and thus noinformation can be written to display device 100. Ground electrode 104can be composed of a transparent conductive material, such as indium tinoxide, or an opaque conductive material. In one example, groundelectrode 104 has a thickness between 5 nm and 1 mm.

Support structure 102 can be composed of a transparent material or anopaque material. Support structure 102 can be composed of polyester,plastic, glass, transparent Mylar, or other suitable material. In oneexample, support structure 102 is shaped to provide a display device 100in the form of a gift card, prepaid card, credit card, shelf tag,boarding pass, or shipping label. Support structure 102 can include abar code 130, text 132, or other suitable information on its surface.

Ground access stripe 108 is arranged on a surface 120 of supportstructure 102 and is spaced apart from e-paper display 106. Groundaccess stripe 108 is arranged parallel to a writing direction of e-paperdisplay 106. In one example, ground access stripe 108 is partially orcompletely embedded within surface 120 of support structure 102. Groundaccess stripe 108 extends from a first edge 116 of support structure 102to a second edge 118 of support structure 102 opposite first edge 116.In this example, ground access stripe 108 and imaging surface 114 ofe-paper display 106 are on the same side of display device 100. In otherexamples, ground access stripe 108 and imaging surface 114 of e-paperdisplay 106 can be on opposite sides of display device 100.

Ground access stripe 108 is composed of any suitable electricallyconductive material, such as a metal or a printed layer (e.g., digitallyprinted or screen printed) of conductive ink. In one example, groundaccess stripe 108 and conductor 110 are composed of a conductivepolymer. In one example, the width, indicated at 124, of ground accessstripe 108 is between 1 mm and 15 mm and the thickness, indicated at126, is between 5 nm and 1 mm. In the example where ground access stripe108 and conductor 110 are composed of a conductive polymer, the entiresupport structure 102 may be composed of the conductive polymer. In oneexample, the conductive polymer has a resistivity between 10⁸ Ohm-cm and10¹¹ Ohm-cm, which is sufficient for writing and erasing currentsbetween 25 μA and 100 μA.

FIG. 2A illustrates a cross-sectional view and FIG. 2B illustrates a topview of one example of a display device 200. Display device 200 includesa support structure 202, a structural window 228, a ground electrode204, an e-paper display 206, and a ground access stripe 208. Groundaccess stripe 208 is electrically coupled to ground electrode 204. Inthis example, the viewing side of display device 200 is indicated by aviewer 222. E-paper display 206 includes an imaging surface 214 and asurface 212 opposite imaging surface 214. Surface 212 contacts groundelectrode 204. Ground electrode 204 and e-paper display 206 aresurrounded by support structure 202.

Structural window 228 extends through support structure 202 so that aviewer 222 can see the image (e.g., image 236) on e-paper display 206.Structural window 228 can be an air gap or be composed of glass,transparent plastic, or other suitable transparent material. Supportstructure 202 defines a frame having a thickness indicated at 224 thatprovides a recessed imaging surface 214 with respect to supportstructure 202. In one example, the thickness 224 of the frame is between100 μm and 300 μm.

Ground access stripe 208 is arranged on the outer edge surface 234 ofsupport structure 202 and surrounds support structure 202. Edge surface234 of support structure 202 is substantially orthogonal to imagingsurface 214. Ground access stripe 208 is composed of any suitableelectrically conductive material, such as a metal or a printed layer(e.g., digitally printed or screen printed) of conductive ink. In oneexample, ground access stripe 208 is composed of a conductive polymer.In one example, ground access stripe 208 has a thickness, as indicatedat 226, between 5 nm and 1 mm. In the example where ground access stripe208 is composed of a conductive polymer, the entire support structure202 may be composed of the conductive polymer. In one example, theconductive polymer has a resistivity between 10⁸ Ohm-cm and 10¹¹ Ohm-cm,which is sufficient for writing and erasing currents between 25 μA and100 μA.

Ground access stripe 208 is likely to be contacted by a user whendisplay device 200 is handled. This contact between a user and groundaccess stripe 208 provides a positive consequence in that if the user isstoring any electrostatic charge, display device 200 will beequipotential with the user, thus minimizing the chance of accidentalimage modifications due to electrostatic discharges.

FIG. 3 illustrates a cross-sectional view of one example of an e-paperdisplay 300. In one example, e-paper display 300 is used for e-paperdisplay 106 or 206 previously described and illustrated with referenceto FIGS. 1A-1B, and 2A-2B, respectively. E-paper display 300 includes aground electrode 302, an active layer 304, and a transparent chargereceiving layer 306. Active layer 304 includes microcapsules 308encapsulated by a resin or polymer 314. In one example, eachmicrocapsule 308 includes black particles 310 and white particles 312suspended in a fluid medium 316. Surface 307 of charge receiving layer306 provides the imaging surface for e-paper display 300 and is also theviewing side for a viewer 318 in this example.

Ambient light is transmitted through charge receiving layer 306, strikesmicrocapsules 308, and is reflected back to the viewer 318. When whiteparticles 312 of a microcapsule 308 are located near charge receivinglayer 306, the microcapsule appears white to the viewer 318. When blackparticles 310 of a microcapsule 308 are located near charge receivinglayer 306, the microcapsule appears black to the viewer 318. Theparticles 310 and 312 have opposite charges. For example, blackparticles 310 can be positively charged particles, and white particles312 can be negatively charged particles. Various shades of gray can becreated by varying the arrangement of alternating microcapsules withwhite and black particles located near charge receiving layer 306 toproduce halftoning.

Microcapsules 308 exhibit image stability using chemical adhesionbetween particles and/or between the particles and the microcapsulesurface. For example, microcapsules 308 can hold text and imagesindefinitely without using electricity, while allowing the text orimages to be changed later.

The structure, materials, and dimensions of the various layers andcomponents of e-paper display 300 can be adapted to specific designcriteria. In one example, the transparent charge receiving layer 306 canbe composed of a transparent polymer and can have a thickness between 50μm and 250 μm. The transparent charge receiving layer 306 can also becomposed of a material that holds charges or is porous or semi-porous tocharges and/or ions.

The diameter of each microcapsule 308 is substantially constant withine-paper display 300 and can be in one example between 20 μm and 100 μm,such as 50 μm. Conductive ground electrode 302 can be composed of atransparent conductive material, such as indium tin oxide, or an opaquematerial. In one example, ground electrode 302 has a thickness between10 nm and 1 mm, or larger depending on how e-paper display 300 is to beused.

In other examples, E-paper display 300 has a variety of otherconfigurations. For example, each microcapsule 308 may include blackparticles suspended in a white colored fluid. The black particles can bepositively charged particles or negatively charged particles. One ormore microcapsules form a pixel of black and white images displayed one-paper display 300. The black and white images are created by placingblack particles near or away from charge receiving layer 306. Forexample, the microcapsules with black particles located away from chargereceiving layer 306 reflect white light, corresponding to a whiteportion of an image displayed on e-paper display 300. In contrast, themicrocapsules with black particles located near charge receiving layer306 appear black to a viewer 318 corresponding to a black portion of theimage displayed on e-paper display 300. Various shades of gray can becreated by using halftoning with black particles located near or awayfrom charge receiving layer 306.

Charge receiving layer 306 may be tinted with alternating blue, red, andgreen regions. Adjacent blue, red, and green regions form color pixels.Color images are created by placing different combinations of white orblack particles near charge receiving layer 306. For example, themicrocapsules of a color pixel with white particles located near the redand green regions of charge receiving layer 306 reflect red and greenlight from e-paper display 300. The viewer 318 will perceive thiscombination as a yellow pixel. When the black particles in themicrocapsules are located near charge receiving layer 306, that colorpixel will appear black to the viewer 318. Additionally oralternatively, the black particles 310 of each microcapsule can bereplaced by blue, red, or green positively or negatively chargedparticles. The particles can be used alone or in combination with atinted charge receiving layer 306 to create a desired color image.

FIG. 4 illustrates one example of a writing module 400. Writing module400 can be used to write information to display device 100 and/or 200previously described and illustrated with reference to FIGS. 1A-1B and2A-2B, respectively. Writing module 400 includes an imaging unit 401including a corona writing unit 402 and a corona erasing unit 406, andconductive roller(s) or brush 412. Conductive roller(s) or brush 412 iselectrically coupled to imaging unit 401 through signal path 410. Coronawriting unit 402 and corona erasing unit 406 are located on the sameside of imaging unit 401.

Corona erasing unit 406 selectivity ejects negative ions 408 toward animaging surface of an e-paper display to erase any text and/or images onthe e-paper display by repelling the negatively charged particles and/orby attracting the positively charged particles within the e-paperdisplay toward the imaging surface. Corona writing unit 402 selectivelyejects positive ions 404 toward an imaging surface of an e-paper displayto write desired text and/or images on the e-paper display by repellingthe positively charged particles and/or by attracting the negativelycharged particles within the e-paper display toward the imaging surface.

Conductive roller(s) or brush 412 makes contact with the ground accessstripe of a display device during writing of the display device toprovide an electrical connection to the ground electrode of the displaydevice. When using conductive roller(s), the roller(s) can also set thespacing between corona writing unit 402 and corona erasing unit 406 andthe display device during writing of the display device. The conductiveroller(s) are composed of any suitable electrically conductive material,such as a metal or conductive rubber. When using a conductive brush, thebrush is composed of any suitable electrically conductive material, suchas a metal or carbon.

FIGS. 5A-5C illustrate one example of a system 420 including a writingmodule 400 a and a display device 100. Writing module 400 a is similarto writing module 400 previously described and illustrated withreference to FIG. 4 , and display device 100 was previously describedand illustrated with reference to FIGS. 1A-1B. In this example, writingmodule 400 a includes a conductive roller 412 a. To write to displaydevice 100, writing module 400 a is brought into contact with displaydevice 100 so that conductive roller 412 a contacts ground access stripe108 as best illustrated in the top view of FIG. 5B and the side view ofFIG. 5C. Conductive roller 412 a electrically couples imaging unit 401to ground electrode 104 via ground access stripe 108 and conductor 110.

Writing module 400 a can be moved in the direction indicated by arrow422 and display device 100 can be held stationary, display device 100can be moved in the opposite direction indicated by arrow 422 andwriting module 400 a can be held stationary, or display device 100 andwriting module 400 a can be moved simultaneously with respect to eachother. While writing module 400 a and display device 100 are movedrelative to each other, conductive roller 412 a maintains contact toground access stripe 108 during the writing of e-paper display 106.

In this example, e-paper display 106 of display device 100 includesmicrocapsules including positively charged black particles andnegatively charged white particles. Corona erasing unit 406 erases anyinformation stored in the microcapsules prior to writing informationwith corona writing unit 402. As display device 100 passes under imagingunit 401, corona erasing unit 406 ejects negative ions 408 onto imagingsurface 114. The negative ions 408 repel negatively charged whiteparticles away from imaging surface 114 and attract positively chargedblack particles toward imaging surface 114. By passing corona erasingunit 406 over imaging surface 114, any information previously written todisplay device 100 is erased by positioning the positively charged blackparticles near the top of the microcapsules and pushing the negativelycharged white particles to the bottom of the microcapsules.

Corona writing unit 402 writes information to the microcapsules. Asdisplay device 100 passes under imaging unit 401, corona writing unit402 selectively ejects positive ions 404 toward imaging surface 114 whena region of display device 100 is to be changed from black to white. Thepositive ions 404 repel positively charged black particles away fromimaging surface 114 and attract negatively charged white particlestoward imaging surface 114. By passing corona writing unit 402 overimaging surface 114 and selectively ejecting positive ions onto imagingsurface 114, information is written to display device 100 by selectivelypositioning negatively charged white particles near the top of themicrocapsules and selectively pushing the positively charged blackparticles to the bottom of the microcapsules.

FIGS. 6A-6C illustrate one example of a system 440 including a writingmodule 400 b and a display device 100. Writing module 400 b is similarto writing module 400 previously described and illustrated withreference to FIG. 4 , and display device 100 was previously describedand illustrated with reference to FIGS. 1A-1B. In this example, writingmodule 400 b includes a conductive brush 412 b. To write to displaydevice 100, writing module 400 b is brought into contact with displaydevice 100 so that conductive brush 412 b contacts ground access stripe108 as best illustrated in the top view of FIG. 6B and the side view ofFIG. 6C. Conductive brush 412 b electrically couples imaging unit 401 toground electrode 104 via ground access stripe 108 and conductor 110.System 440 writes to display device 100 similarly to system 420previously described and illustrated with reference to FIGS. 5A-5C.

FIGS. 7A-7C illustrate one example of a system 460 including a writingmodule 400 c and a display device 200. Writing module 400 c is similarto writing module 400 previously described and illustrated withreference to FIG. 4 , and display device 200 was previously describedand illustrated with reference to FIGS. 2A-2B. In this example, writingmodule 400 c includes a plurality of conductive rollers 412 c. To writeto display device 200, writing module 400 c is brought into contact withdisplay device 200 so that conductive rollers 412 c contact groundaccess stripe 208 on opposite sides of display device 200 as bestillustrated in the top view of FIG. 7B and the side view of FIG. 7C.Conductive rollers 412 c electrically couple imaging unit 401 to groundelectrode 204 via ground access stripe 208. Conductive rollers 412 calso constrain the motion of display device 200 so that the displaydevice travels along the desired path. System 460 writes to displaydevice 200 similarly to system 420 previously described and illustratedwith reference to FIGS. 5A-5C.

By including a ground access stripe on a display device, an electricalconnection between the writing module and the ground electrode of thedisplay device can be maintained during movement of the writing moduleand the display device relative to each other. The ground access stripealso improves image robustness of the display device by providing aconductive path to ground to prevent accidental electrostatic dischargesfrom users from altering the image.

Although specific examples have been illustrated and described herein, avariety of alternate and/or equivalent implementations may besubstituted for the specific examples shown and described withoutdeparting from the scope of the present disclosure. This application isintended to cover any adaptations or variations of the specific examplesdiscussed herein. Therefore, it is intended that this disclosure belimited only by the claims and the equivalents thereof.

The invention claimed is:
 1. A display device comprising: an electronicpaper display imageable by receiving charges on a charge receiving layerof the electronic paper display; a ground electrode opposite to thecharge receiving layer of the electronic paper display; and a groundaccess stripe electrically coupled to the ground electrode, the groundaccess stripe exposed completely around the display device on the outeredge of the display device and substantially orthogonal to theelectronic paper display.
 2. The display device of claim 1, wherein theground electrode comprises a transparent conductive material.
 3. Thedisplay device of claim 1, wherein the ground electrode comprises anopaque conductive material.
 4. The display device of claim 1, whereinthe ground electrode allows charges received on the charge receivinglayer during writing of the electronic paper display to flow to theground electrode.
 5. The display device of claim 1, wherein theelectronic paper display comprises an active layer between the chargereceiving layer and the ground electrode.
 6. The display device of claim5, wherein the active layer comprises microcapsules comprising blackparticles and white particles suspended in a fluid medium.
 7. A displaydevice comprising: a support structure; a ground electrode arranged onthe support structure; an electronic paper display arranged on theground electrode, the electronic paper display imageable by receivingcharges on a charge receiving layer of the electronic paper display; anda ground access stripe electrically coupled to the ground electrode, theground access stripe exposed completely around the support structure onthe outer edge of the support structure and substantially orthogonal tothe electronic paper display.
 8. The display device of claim 7, whereinthe charge receiving layer is recessed with respect to the supportstructure.
 9. The display device of claim 7, wherein the supportstructure comprises a conductive polymer.
 10. The display device ofclaim 7, wherein the ground electrode allows charges received on thecharge receiving layer during writing of the electronic paper display toflow to the ground electrode.
 11. The display device of claim 7, whereinthe charge receiving layer is tinted with alternating blue, red, andgreen regions, and wherein adjacent blue, red, and green regions formcolor pixels.
 12. A system comprising: a writing module comprising awriting unit, a first conductive roller, and a second conductive roller,the writing module to write to a display device, the display devicecomprising: a support structure; a ground electrode arranged on thesupport structure and exposed at an edge of the support structure; andan electronic paper display arranged on the ground electrode, theelectronic paper display imageable by receiving charges on a chargereceiving layer of the electronic paper display from the writing unit,wherein the first conductive roller and the second conductive roller areto contact the ground electrode to provide a ground return path thatallows charges received on the charge receiving layer to flow to theground electrode during writing of the electronic paper display as thewriting module and the display device are moved relative to each other.13. The display device of claim 12, wherein the first conductive rolleris to contact the ground electrode on a first side of the display deviceand the second conductive roller is to contact the ground electrode on asecond side of the display device opposite to the first side.
 14. Thedisplay device of claim 12, wherein the writing module further comprisesa third conductive roller and a fourth conductive roller to contact theground electrode to provide the ground return path that allows chargesreceived on the charge receiving layer to flow to the ground electrodeduring writing of the electronic paper display as the writing module andthe display device are moved relative to each other.
 15. The displaydevice of claim 14, wherein the first conductive roller and the secondconductive roller are to contact the ground electrode on a first side ofthe display device and the third conductive roller and the fourthconductive roller are to contact the ground electrode on a second sideof the display device opposite to the first side.
 16. The display deviceof claim 12, wherein the writing module further comprises an erasingunit to erase any text and/or images on the electronic paper display.17. The display device of claim 12, wherein the support structurecomprises a conductive polymer.